ABSTRACT: Tissue and organ function has been conventionally understood in terms of the interactions among discrete and homogeneous cell types. This approach has proven difficult in neuroscience due to the marked diversity across different neuron classes, but may also be further hampered by prominent within-class variability. Here, we considered a well-defined, canonical neuronal population – hippocampal CA1 pyramidal cells – and systematically examined the extent and spatial rules of transcriptional heterogeneity. Using next-generation RNA sequencing, we identified striking variability in CA1 PCs, such that the differences along the dorsal-ventral axis rivaled differences across distinct pyramidal neuron classes. This variability emerged from a spectrum of continuous expression gradients, producing a profile consistent with a multifarious continuum of cells. This work reveals an unexpected amount of variability within a canonical and narrowly defined neuronal population and suggests that continuous, within-class heterogeneity may be an important feature of neural circuits. Hippocampal RNA profiles were generated by deep sequencing on Illumina HiSeq 2500, with three biological replicates per population
Project description:The subcellular localization and translation of messenger RNA (mRNA) supports functional differentiation between cellular compartments. In neuronal dendrites, local translation of mRNA provides a rapid and specific mechanism for synaptic plasticity and memory formation, and might be involved in the pathophysiology of certain brain disorders. Despite the importance of dendritic mRNA translation, little is known about which mRNAs can be translated in dendrites in vivo and when their translation occurs. Here we collect ribosome-bound mRNA from the dendrites of CA1 pyramidal neurons in the adult mouse hippocampus. We find that dendritic mRNA rapidly associates with ribosomes following a novel experience consisting of a contextual fear conditioning trial. High throughput RNA sequencing followed by machine learning classification reveals an unexpected breadth of ribosome-bound dendritic mRNAs, including mRNAs expected to be entirely somatic. Our findings are in agreement with a mechanism of synaptic plasticity that engages the acute local translation of functionally diverse dendritic mRNAs. RNA-Seq of ribosome-bound mRNA immunoprecipitated from dendrites and soma of CA1 pyramidal neurons in the mouse hippocampus
Project description:The transcriptional repressor Zbtb20 is essential for specification of hippocampal CA1 pyramidal neurons. Moreover, ectopic expression of Zbtb20 is sufficient to transform subicular and retrosplenial areas of D6/Zbtb20S mice to CA1. We used microarrays to identify genes that are repressed by Zbtb20 in developing CA1 pyramidal neurons in the CA1-transformed cortex of D6/Zbtb20S mice. For RNA extraction and hybridization on Affymetrix microarrays, we isolated the CA1-transformed subiculum and retrosplenial cortex from postnatal day 1 D6/Zbtb20S mice, as well as corresponding areas from their wildtype littermates. Total RNA was extracted using the RNeasy Lipid Tissue Mini Kit (Qiagen). Each RNA sample represents a pool of RNA obtained from dissected tissues of seven animals.
Project description:We studied the transcriptomes of mouse CA1 inhibitory cells. Novel clustering methods identified all 23 previously described CA1 inhibitory types, while also suggesting 6 new inhibitory classes. Latent‐factor analysis revealed a common continuum of expression of many genes within and between classes, which we hypothesized correlates with a continuum from faster‐spiking cells that proximally target pyramidal cells, to slower active cells targeting pyramidal distal dendrites or interneurons. Overall design: 6971 single cells isolated from the mouse cortex CA1 region
Project description:Comparing WT mice to a mouse model of mental retardation, this work identifies genes which display differences in ribosome-bound mRNAs, in hippocampus CA1 pyramidal cells. These genes products are potent functional components of neuronal plasticity and hippocampus-dependent memory. Overall design: Using a triple transgenic mouse line, we immunoprecipitated the HA-Rpl22 protein to isolate and sequence ribosome-associated mRNA in CA1 pyramidal cells. Pairwise comparison of wild type and Fmr1 KO mice defined a specific gene expression profile.
Project description:Gene expression profiling of nuclei isolated from genetically defined neuronal subpopulations of the adult Drosophila brain. Gene expression profiles were generated from nuclei isolated from all neurons (R57C10-GAL4), Kenyon cells (OK107-GAL4), and octopaminergic (Tdc2-GAL4) neurons in the adult Drosophila head using a method similar to INTACT (Deal and Henikoff, 2010; Steinner et al., 2012). Sequencing was performed with an Illumina HiSeq 2000.
Project description:The reprogramming of differentiated cells to an embryonic stem cell-like state provides a powerful system to explore fundamental mechanisms of development, including how mammalian cells establish and maintain pluripotency and long-term self-renewal capability. Based on the similarities between embryonic stem cells and cancer cells, we investigated the potential role of the retinoblastoma tumor suppressor and cell cycle regulator RB in the reprogramming of fibroblasts into induced pluripotent stem cells (iPS cells). Herein we demonstrate that loss of RB function leads to both an acceleration of the reprogramming process and the generation of more iPS clones from fibroblasts. This effect is largely due to a restrictive role for RB at the early stages of reprogramming. Surprisingly, however, RB inactivation does not enhance the formation of iPS clones by accelerating the proliferation of cells undergoing reprogramming. Rather, a genome-wide investigation of RB targets indicates that RB binds to regulatory regions of pluripotency genes such as Sox2 and Oct4 and contributes to their full repression in differentiated cells. This effect correlates with the maintenance of a repressive chromatin structure at these loci. Accordingly, Rb-deficient fibroblasts can be reprogrammed into iPS cells even in the absence of exogenous Sox2, which is normally required to initiate reprogramming from fibroblasts. These experiments identify a novel barrier in the reprogramming process, mainly the repression of certain pluripotency genes such as Sox2 by RB, which provides a new link between tumor suppressor mechanisms and cellular reprogramming. RNAseq from MEFs with 2 biological replicates (save CP), Rb ChIPseq from MEFs with 2 biological replicates, Histone H3 modification ChIPseq from MEFs with 1 biological replicate
Project description:Neurodegenerative brain disorders become more common in the aged. Most of these disorders are associated with or caused by selective death of certain neuronal subpopulations. The mechanisms underlying the differential vulnerability of certain neuronal populations are still largely unexplored and few neuroprotective treatments are available to date. Elucidation of these mechanisms may lead to a greater understanding of the pathogenesis and treatment of neurodegenerative diseases. Moreover, preconditioning by a short seizure confers neuroprotection following a subsequent prolonged seizure. Our goal is to identify pathways that confer vulnerability and resistance to neurotoxic conditions by comparing the basal and preconditioned gene expression profiles of three differentially vulnerable hippocampal neuron populations. Hippocampal CA1 and CA3 pyramidal neurons are highly susceptible to seizures and ischemia, whereas dentate gyrus granule cells are relatively resistant. A brief preconditioning seizure confers protection to the pyramidal cells. We will first determine gene expression profiles of untreated rat CA1 and CA3 pyramidal cells, and dentate granule cells, using laser capture microscopy to obtain region-specific neuronal mRNA. We will then determine the effect of a brief preconditioning seizure, which is neuroprotective in CA1 and CA3, on these expression profiles. We hypothesize that common molecular mechanisms exist in neurons that determine their susceptibility to seizure-induced injury. Intrinsic differences in gene expression exist between hippocampal glutamatergic CA1 and CA3 pyramidal neurons, on the one hand, and dentate granule cells on the other, which contribute to the greater susceptibility of pyramidal neurons to degeneration in experimental stroke and epilepsy. We specifically hypothesize that differences in basal energy metabolism genes may confer differential susceptibility to neurodegeneration produced by seizures and ischemia. Anesthetized animals will be sacrificed by decapitation, and frozen 10 micron sections will be lightly stained with cresyl violet to identify cell layers in the hippocampus. Approximately 1000 neurons from each of the three cell layers will be isolated by LCM. Poly-A RNA will be amplified using a modified Eberwine protocol. The quality of our aRNA will be evaluated by quantitative RT-PCR of GluR6 and KA2 mRNA levels before we send the samples to the Center for labeling and hybridization to Affymetrix rat 230A arrays. We will provide a one-round amplification cDNA product to the center for labeling and hybridization. This protocol is identical to a previously approved study by Jim Greene in our laboratory.
Project description:Recent advances in single-cell RNAseq technologies are enabling new cell type classifications. For neurons, electrophysiological properties traditionally guide cell type classification but correlating RNAseq data with electrophysiological parameters has been difficult. Here we demonstrate RNAseq of electrophysiologically and synaptically characterized individual, patched neurons in the hippocampal CA1-region and subiculum, and relate the resulting transcriptome data to their electrical and synaptic properties. In this analysis, we explored the hypothesis that precise combinatorial interactions between matching cell-adhesion and signaling molecules shape synapse specificity. In analyzing interneurons and pyramidal neurons that are synaptically connected, we identified two independent, developmentally regulated networks of interacting genes encoding cell-adhesion, exocytosis and signal-transduction molecules. In this manner, our data allow postulating a presumed cell-adhesion and signaling code, which may explain neuronal connectivity at the molecular level. Our approach enables correlating electrophysiological with molecular properties of neurons, and suggests new avenues towards understanding synaptic specificity. Overall design: These data include 15 tissue samples (including 3 independent replicas in 5 developmental stages) as well as 93 single-cell samples (including CA1 cholecystokinin, parvalbumin, and pyramidal neurons as well as subiculum burst and regular firing pyramidal neurons).
Project description:Flow sorted CD3+CD8+CD44+CXCR3+NKG2D+ lymph node cells from C3H/HeJ mice with alopecia were flow sorted and profiled in relation to CD3+CD8+CD44+CXCR3+NKG2D- lymph node cells from the same host Cell populations were sorted from three separate mice
Project description:Whereas cloning mammals by direct somatic cell nuclear transfer has been successful using a wide range of donor cell types, neurons from adult brain remain “unclonable” for unknown reasons. Here we examined whether neurons from adult mice could be cloned, using a combination of two epigenetic approaches. First, we used a specific antibody to discover cell types with reduced amounts of a repressive histone mark - dimethylated histone H3 lysine 9 (H3K9me2) - and identified CA1 pyramidal cells in the hippocampus and Purkinje cells in the cerebellum as candidates. Second, reconstructed embryos were treated with trichostatin A (TSA), a potent histone deacetylase inhibitor. Using CA1 cells, cloned offspring were obtained at high rates, reaching 10.2% and 4.6% (per embryos transferred) for male and female donors, respectively. Cerebellar Purkinje cell nuclei were too large to maintain their genetic integrity during nuclear transfer, leading to developmental arrest of embryos. However, gene expression analysis using cloned blastocysts corroborated a high rate of genomic reprogrammability of CA1 pyramidal and Purkinje cells. Neurons from the hippocampal dentate gyrus and cerebral cortex, which had higher amounts of H3K9me2, could also be used for producing cloned offspring, but the efficiencies were low. A more thorough analysis revealed that TSA treatment was essential for cloning adult neuronal cells. This study demonstrated for the first time that adult neurons could be cloned by nuclear transfer. Furthermore, our data imply that reduced amounts of H3K9me2 and increased histone acetylation appear to act synergistically to improve the development of cloned embryos. Comparative gene expression analyses using blastocysts of cloned embryos were performed by microarray. Cloned embryos were produced with three different types of donor cells (neonatal Sertoli cells, CA1 pyramidal cells and Purkinje cells) and all cloned embryos were treated with Trichostatin A (TSA). Each embryos were cultured for 96 h and blastocysts derived from each donor cell types were subjected to gene expression microarray. For comparison of gene expression, the data sets of control sex- and genotype-matched embryos produced by in vitro fertilization and SCNT-derived blastocysts from cumulus cells treated with TSA from our previous paper (Inoue K. et al. Science 2010) were also used.